The present invention relates to a windshield wiper control system for a vehicle. More particularly, the present invention relates to a low-cost windshield wiper control system which may be configured in a plurality of ways.
In recent years, it has been increasingly common for motor vehicles to incorporate rain sensing wiper control systems that adjust the speed of the wipers in response to the accumulation of water on the outside surface of the windshield. This is especially true of luxury motor vehicles. Most commonly, these systems employ an optical rain sensor to detect the presence of water on the windshield glass. The presence of rain or snow on the outside surface of the windshield disrupts light beams emitted by the optical sensor, and the rain sensor detects such disruptions to determine an appropriate speed for the vehicle wipers. A practical implementation of such a system was taught by Teder in U.S. Pat. No. 5,059,877. The rain sensor taught in U.S. Pat. No. 5,898,183 to Teder shows a rain sensor may be made in a very compact and inexpensive form.
The sensor, however, represents only part of a complete rain sensing windshield wiper control system. The sensor must be operatively connected to a windshield wiper motor which, in turn, is connected to a wiper linkage that runs the wipers to keep the windshield clear of water. In most modern rain sensing wiper systems, communication from the sensor is typically done in digital form over a multiplexed system such as a Local Interconnect Network (“LIN”) or Controller Area Network (“CAN”) bus. Indeed, the trend in most vehicle wiring has been towards more use of such multiplexed systems for a variety of purposes. These allow for greater system integration and intercommunication, improved system diagnostics, as well as other advantages. Many luxury vehicles use these multiplexed systems in almost all systems and subsystems. It is no surprise, therefore, that almost all currently produced factory-installed rain sensing windshield wiper systems are built around the CAN and LIN bus architectures.
With all the advantages of multiplexed systems noted above, a critical disadvantage is the cost of such systems. Cost, typically is the single biggest driver as to whether or not a particular convenience feature is included as a standard feature or offered as an option on any particular vehicle. As result, there are currently no low-cost cars sold in North America that offer rain sensing windshield wipers, even as part of an option package.
One lower cost alternative to a LIN or CAN based system is to put an interface module between the wiper motor and the switch, for example as taught by Teder in U.S. Pat. No. 5,239,244. An interface module may include relays that directly supply current to the wiper motor. A similar device is sold by Opto-Electronic Design under the trademark “Rain Tracker.” This approach is markedly less expensive than a CAN approach, but the interface module still has the expense of a plastic housing, relays, etc. Also, there is reluctance on the part of the vehicle manufacturer to proliferate ever more small control modules under the dashboard.
Alternatively, manufacturers may integrate a computer-based rain sensor interface, with or without CAN communications, directly into the wiper motor housing. This has been done, for example, in many production General Motors vehicles sold in the mid-1990's with rain sensing windshield wiper control systems. The control circuit was enclosed in a suitable weatherproof enclosure for the electronic circuitry, as the under-hood environment of the wiper motor can be quite harsh. The electronic circuitry must thus also be designed to withstand an extended temperature range. Also, the connection to the sensor must be made through the vehicle firewall. This approach works well, but is not low cost.
It is a common configuration in currently produced low-cost cars to include a simple intermittent wiper control system built into the windshield wiper operation switch instead of the wiper motor. The general trend has been away from such systems, partly because the space for the wiper switch is crowded by the need for a large airbag assembly built into the steering wheel hub. One such system is taught by Uchiayama in U.S. Pat. No. 5,708,242. This system does not accept a rain sensor input, however, and the physical size limits imposed upon the wiper switch would make it difficult to increase the complexity of the system.
The trend in vehicle wiring systems and rain sensing wiper control systems is thus towards greater complexity, and this will likely evolve over time to become affordable. Today, however, in order to provide the convenience of rain sensing wipers for low-cost cars and vehicles sold in emerging markets, a truly simple and inexpensive complete rain sensing wiper system is needed.